1. Field of the Invention
The present invention relates to a solution treatment unit which performs, for example, developing treatment on, for example, a substrate and a filter unit included in the solution treatment unit.
2. Description of the Related Art
A mask for forming a circuit pattern on the surface of a semiconductor wafer (described as a wafer hereinafter) is obtained by irradiating a resist face with light, an electron beam, an ion beam or the like and performing developing treatment thereon after coating the surface of the wafer with a resist. A developing step of these steps is to dissolve portions which are irradiated with light or the like, or portions which are not irradiated with the same in an exposing step, with an alkaline aqueous solution or the like, and is performed by a method shown in FIG. 10 conventionally.
Namely, in a conventional method, a wafer w is adsorbed and held on a spin chuck 11 having a function of vacuum adsorption, and a supply nozzle 13, in which a large number of discharge holes 12 are arranged over a length corresponding to a diameter of the wafer W, is positioned so that the discharge holes 12 are spaced, for example, 1 mm above the surface of the wafer W above the central portion of the wafer W. Further, a developing solution 10 is supplied through the discharge holes 12 to the central portion of the surface of the wafer W to perform coating thereof and the wafer is subsequently rotated a half turn (180 degree) while the developing solution 10 is supplied through the discharge holes 12.
In a developing system of this type, as shown in FIG. 11, nitrogen (N2) gas is blown into a tank 14, and the developing solution 10 is delivered with the pressure through a filter portion 15 and a valve 16 and so on, and supplied through the supply nozzle 13 to the wafer W.
The filter portion 15 is to remove, for example, particles or the like mixing into the developing solution 10 by filtering them, and has a structure in which a filter 101 for removing the particles or the like is provided to be connected with a flow path 102 for the developing solution inside of, for example, a case 100, and further an exhaust passage 103 provided with a valve 104 is connected to the upper portion side of the flow path 102. 105 is an electrical capacitance sensor for detecting the generation of bubbles, and 106, 107 are supply flow paths for the developing solution 10.
Incidentally, the pressure is applied to the inside of the tank 14 by the N2 gas as described above in this supply system of the developing solution 10, whereby the N2 is dissolved in the developing solution 10 delivered with the application of pressure. Since a volume of the case 100 is larger than that of the supply flow path 106 for the developing solution 10 in the filter portion 15, the developing solution 10 is under reduced pressure when flowing from the supply flow path 106 into the case 100, and the N2 dissolved in the developing solution 10 is vaporized to generate minute bubbles (micro bubbles) with the difference in pressure.
Due to such bubbles mixing into the developing solution 10, the flow amount of the developing solution 10 varies by the amount of the bubbles present therein, the filtering precision of the filter 101 deteriorates due to the bubbles adhering thereto in the filter portion 15, and an insufficient or no reaction occurs between the developing solution and a resist in portions in which the bubbles are mixing when the developing solution 10 is coated on the wafer W, thereby causing developing defects.
Conventionally, therefore, the bubbles generated in the filter portion 15 are removed together with the developing solution 10 through the exhaust passage 103 by manually opening the valve 104. The electrical capacitance sensor 105 is set to be on when the amount of the bubbles increases equal to or greater than a standard value and set to be off when the amount of the bubbles is smaller than or equal to the standard value, and the opening and closing timing of the valve 104 is performed based on the on-off signal of the sensor 105.
However, the above-described technique has disadvantages that the developing solution 10 containing the bubbles is exhausted together with the bubbles, thereby increasing the amount of the drained developing solution 10 and total consumption of the developing solution 10.
An object of the present invention is to provide a filter unit and a solution treatment unit capable of reducing consumption of a treatment solution.
To achieve this object, in a filter unit according to the present invention for removing impurities and bubbles contained in a treatment solution comprising: an impurity filter for removing the impurities; a flow path for flowing the treatment solution into the impurity filter; an exhaust passage for exhausting gas to the outside of the filter unit, which is connected to the flow path; and a bubble filter provided inside of the exhaust passage or on a connecting portion between the exhaust passage and the flow path to block the exhaust passage, the bubble filter has a function of blocking transmission of liquid and transmitting gas, whereby the bubbles are removed from the treatment solution by making the bubbles contained in the treatment solution pass through the bubble filter. In such filter unit, only the bubbles can be removed from the treatment solution, whereby the treatment solution is not drained, enabling consumption of the treatment solution to be reduced.
It is preferable now to use a hollow fiber a membrane for the bubble filter, and in this case, the bubbles can be efficiently removed since a large contact area can be secured in a small volume in the hollow fiber membrane. Additionally, it may be structured that means for generating ultrasound is provided on the outside of the flow path, and dissolved gas contained in the treatment solution is forced to vaporize to generate the bubbles by giving ultrasonic vibration to the treatment solution flowing in the flow path, which makes it possible to remove also the dissolved gas, enabling the amount of the dissolved gas contained in the treatment solution to be further reduced.
Further, the filter unit may have a structure in which the flow path is formed in a ring shape so that the treatment solution flows from down upward therein, the impurity filter is provided on the inside of the flow path, and the exhaust passage is further provided on the upper portion side of the flow path, which enables the amount of the removed bubbles to be increased. Furthermore, a pressure in the exhaust passage may be lower than that of the flow path, which makes it possible to remove not only the bubbles contained in the treatment solution but also the dissolved gas, enabling the amount of the dissolved gas contained in the treatment solution to be reduced.
The solution treatment unit incorporating such filter unit is structured so that the treatment solution removed the impurities and the bubbles therefrom in the filter unit is supplied through a supply nozzle to the surface of a substrate held substantially horizontal by a substrate holding portion to form a treatment solution film on the surface of the substrate.
Moreover, a solution treatment unit according to the present, in which bubbles contained in a treatment solution from a treatment solution tank are removed in an intermediate tank, and the treatment solution is supplied through a supply nozzle to the surface of a substrate held substantially horizontal by a substrate holding portion to form a treatment solution film on the surface of the substrate, may be structured so that the intermediate tank comprises: an exhaust passage for exhausting gas to the outside of the intermediate tank; and a bubble filter provided inside of the exhaust passage or on a connecting portion between the exhaust passage and the flow path to block the exhaust passage, and the bubble filter has a function of blocking transmission of liquid and transmitting gas, whereby the bubbles are removed from the treatment solution by making the bubbles contained in the treatment solution pass through the bubble filter. Also in this case, a reduction in consumption of the treatment solution is made possible since only the bubbles can be removed from the treatment solution. On this occasion, a developing solution is given as an example of the treatment solution.
These objects, other objects and advantages of the present invention will become readily apparent by the following description and the accompanying drawings.